refactoring: extract POST data used in tests
refactoring: extract POST data used in tests

before implementing #21

geometalab/osmaxx-frontend,geometalab/osmaxx,geometalab/osmaxx-frontend,geometalab/osmaxx,geometalab/drf-utm-zone-info,geometalab/osmaxx-frontend,geometalab/osmaxx-frontend,geometalab/osmaxx,geometalab/drf-utm-zone-info,geometalab/osmaxx